1. Field of the Invention
The present invention relates to a storage module or capacitor module which incorporates a plurality of storage means and can transfer energy among the storage means.
2. Description of the Related Art
As a conventional apparatus which can transfer electric energy stored in a storage means, a transfer apparatus 31 disclosed in e.g. JP-A-7-322516 is well-known. As shown in FIG. 8, the transfer apparatus 31 is configured so that the energy stored in a plurality of capacitors C1-C4 can be averaged by transferring the energy stored in an any one of these capacitors to the other capacitors. Specifically, the transfer apparatus 31 includes a series circuit of a choke coil L1 and switch SW1 which is connected in parallel to the capacitor C1; a switch 21 connected to the capacitor C2 through the choke coil L1; a series circuit of a choke coil L2 and a switch SW22 which is connected in parallel to the capacitor C2; a series circuit of a choke coil L3 and a switch SW32 which is connected to the capacitor C3; a switch SW32 connected to the capacitor C3 through the choke coil L2; and a switch SW4 connected to the capacitor C4 through the choke coil L3.
In this transfer apparatus 31, where the energy stored in the capacitor C4 is transferred to the capacitor C1, first, the switch SW4 is turned on. In this case, as seen from FIG. 8, a current I31 flows to excite the choke coil L3. Next, the switch SW4 and switch SW31 are simultaneously turned on and off, respectively. Then, a current I32 based on the excited energy of the choke coil L3 flows to charge the capacitor C3. Further, after the switch SW31 is turned off, the switch SW32 is turned on. Then, a current I33 flows to excite the choke coil L2. Subsequently, the switch SW32 and switch SW22 are turned on and off, respectively. Then, a current I34 based on the excited energy of the choke coil L2 flows to charge the capacitor C2. Next, after the switch SW22 is turned off, the switch SW21 is turned on. Then, a current I35 flows to excite the choke coil L1. Finally, the switch SW21 and switch SW1 are simultaneously turned off. Then, a current I36 based on the excited energy of the choke coil L1 flows to charge the capacitor C1. In this way, the energy stored in the capacitor C4 is transferred to the capacitor C1.
However, the conventional transfer apparatus 31 described above presents the following problem. Namely, in the transfer apparatus 31, in order to average the stored energy in the capacitors C1-C4, the choke coils L1-L3 and switches SW1-SW4 must be connected. This is very troublesome.
Further, for example, in order to transfer the energy from the capacitor C4 to the capacitor C3, the switch SW4 and switch SW3 must be simultaneously turned off and on, respectively. In this case, if the switch SW31 is turned on prior to turn-off of the switch SW4, the capacitors C3 and C4 are short-circuited through the switches SW4 and SW31 so that the energy stored in both capacitors C3 and C4 is lost. On the other hand, if the switch SW4 is turned off prior to the turn-on of the switch SW31, a very high voltage is generated across the switch SW4 so that the switch SW3 will be damaged. Thus, the conventional transfer apparatus 31 presents a problem that if the timing of the on/off control of the switches SW1-SW4 becomes out of sync slightly, the short-circuiting or damage of the circuit component occurs, and the energy cannot be transferred.
Further, in order to transfer the energy from the capacitor C4 to the capacitor C1, the switches SW4-SW1 must be on/off controlled many times at accurate timings. Therefore, the transfer apparatus 31 also presents a problem that the control of switches is troublesome.
In addition, in the transfer apparatus 31, in order to transfer the energy among the four capacitors C1-C4, six switches SW1-SW4 must be employed. In this case, assuming that energy is transferred among a large number of capacitors, the number of the switches to be used is approximately twice as much as that of the capacitors. Therefore, the conventional transfer apparatus also presents the problem that it requires a large number of switches and hence is expensive and up-sized.
The present invention has been accomplished in order to solve the problems described above, and an object of the present invention is to provide a storage module which can transfer stored energy among a plurality of storage means without making troublesome connecting work. Another object of the present invention is to provide a storage module which can transfer stored energy reliably, surely and easily and can be made inexpensive and down-sized.
In order to attain the above object, according to a first aspect of the present invention, there is provided a storage module comprising: a plurality of storage means for storing electric energy; and energy transfer means for transferring stored energy among the plurality of storage means so that the charging voltage across each of the storage means can be kept at a value according to a prescribed ratio.
According a second aspect of the present invention, there is provided a storage module according to the first aspect, wherein the energy transfer means includes a plurality of series circuits each composed of at least a first winding and switching means connected in series, each of the plurality of series circuits is adapted to be connectable in parallel to each of the plurality of storage means, the first windings are magnetically coupled with one another, and the plurality of switching means are switching-controlled synchronously with one another. In this case, the switching means can be constructed of a field effect transistor or a bipolar transistor.
According to a third aspect of the present invention, there is provided a storage module according to the first aspect or second aspect, wherein a second winding is incorporated or externally attached which is coupled with the first winding and serves to keep the charging voltage across the entire plurality of storage means in each of a plurality of storage modules at a value according to a predetermined ratio.
According to a fourth aspect of the present invention, there is provided a storage module according to any one of the first to third aspect, further comprising coupling means for mechanically coupling itself with other storage means.
According to a fifth aspect of the present invention, there is provided a storage module according to the fourth aspect, wherein the coupling means serves both mechanical coupling and electric connection.